LightingShader and NormalSource comment and style fixes

src/core/SkNormalSource.h

Index: src/core/SkNormalSource.h
diff --git a/src/core/SkNormalSource.h b/src/core/SkNormalSource.h
index 4b09d0b41188531be6c73dce235726bdba82a048..8b11c7af5dee18bc7212978301110b63afe2b408 100644
--- a/src/core/SkNormalSource.h
+++ b/src/core/SkNormalSource.h
@@ -68,7 +68,7 @@ public:
     */
     static sk_sp<SkNormalSource> MakeFromNormalMap(sk_sp<SkShader> map, const SkMatrix& ctm);
 
-    /** Returns a normal source that provides straight-up normals only (0, 0, 1).
+    /** Returns a normal source that provides straight-up normals only <0, 0, 1>.
     */
     static sk_sp<SkNormalSource> MakeFlat();
 
@@ -108,8 +108,10 @@ public:
          */
         kRoundedIn
     };
-    /** Returns a normal source that generates a bevel for the given shape. UNIMPLEMENTED: Will
-        return straight-up normals only.
+    /** Returns a normal source that generates a bevel for the shape being drawn. This normal source
+        works only for shapes whose geometry processors implement distance vectors (as of 2016-08-11

[egdaniel, 2016/08/11 20:21:02]

After the first sentence, I would say "Currently this is not implemented on CPU
rendering. On GPU this currently only works for anti-aliased circles and
rectangles." At this level of the code there isn't a need to go into what
geometry processors are. 

+        only anti-aliased rectangles and circles do this). It is also only implemented in the GPU
+        backend, so rendering must happen on the GPU for this effect to work correctly.
 
         @param  type   the type of bevel to add.
         @param  width  the width of the bevel, in source space. Must be positive.